1. Field of the Invention
The present invention relates to an optical disk for recording copyrighted content information, and a method and an apparatus for reproducing copyrighted content information recorded in an optical disk.
2. Description of the Related Art
In recent multimedia societies, optical disks such as a CD-ROM and a DVD have become remarkably widespread. With the widespread use of the optical disks, a so-called pirated ROM disks have appeared and allows a pirate to benefit from the disk without compensating a copyright owner by fraud by illegally making a pirated copy of the optical disk. The percentage of pirated copies of disks is rapidly increasing. Illegal copying of the optical disk can take place in the following manner. Generally speaking, a pirate purchases an authorized optical disk, makes a master tape by reproducing information recorded on the optical disk by means of a disk drive, and mass-produces the pirated copies from the master tape by the same method as a general disk manufacturing method.
In order to protect against the above-mentioned unauthorized copying, some optical disks are devised so that they can be reproduced by only a player designed specifically for them. As this type of optical disk, for example, there is, disclosed in the Japanese Patent Laid-Open Publication No 7-85574 a method including the steps of recording main information on an optical recording medium using a predetermined coding means, storing key information indicating decoding means for decoding the main information in a form of a barcode symbol in a mirror surface area or the like, reading our the key information by a reproducing apparatus, decoding and reproducing the main information utilizing a coding method indicated by the key information.
The above-mentioned method of protecting against unauthorized copying has such a very excellent advantage that a general optical disk player cannot reproduce the optical disk. However, the method is helpless against and cannot protect against copying means for performing copying involving no reproducing operation, i.e., for physically copying or transferring concavo-convex pits of data of a signal recorded on an optical disk surface as they are. This copying method requires no reproducing means, and can copy concavo-convex pit information of the optical disk as it is even though original data of signal to be recorded on the optical disk is made sophisticated and complicated. Therefore, the above-mentioned method of protecting against unauthorized copying is useless.
An essential object of the present invention is, therefore, to provide an optical disk capable of protecting against copying means for physically copying concavo-convex pits of data of a signal recorded on an optical disk surface as they are.
Another object of the present invention is to further provide an method and apparatus for reproducing information recorded on the optical disk. capable of protecting against copying means for physically copying concavo-convex pits of data of a signal recorded on an optical disk surface as they are.
In order to achieve the aforementioned objective, according to one aspect of the present invention, there is provided an optical disk for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising:
a first area having a reflecting film partly removed; and
a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method.
According to another aspect of the present invention, there is provided an optical disk for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising:
a first area having a reflecting film partly removed;
a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method;
a first area location information recording area for recording location information of the first area on the disk; and
a second area location information recording area for recording location information of the second area on the disk.
In the above-mentioned optical disk, the first area having the reflecting film partly removed is preferably included in a user data recording area for recording user data therein.
In the above-mentioned optical disk, the first area having the reflecting film partly removed preferably includes a portion, which is formed by removing the reflecting film, and which has a length longer than a maximum pit length determined by the requirements of the modulation method, in a circumferential direction of the optical disk.
In the above-mentioned optical disk, each of the pits recorded in the second area is preferably longer than a maximum pit length determined by the modulation method.
In the above-mentioned optical disk, each of the pits recorded in the second area is preferably longer than a maximum pit length determined by the modulation method, and
wherein edges in the center of each of the pits recorded in the second area are inclined more gradually than edges in an end portion of each of the pits.
In the above-mentioned optical disk, the first area location information recording area and the second area location information recording area are preferably recorded in an area except for a user data recording area for recording user data therein.
According to a further aspect of the present invention, there is provided a method for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, and a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method, the method including the steps of:
detecting an area having the reflecting film partly removed, in accordance with a reproduced signal of the first area;
detecting a pit which is different from the pit satisfying the requirements of the predetermined modulation method, in accordance with a reproduced signal of the second area; and
judging whether or not the information recorded on the optical disk should be reproduced, in accordance with results detected by the two steps of detecting.
According to a still further aspect of the present invention, there is provided a method for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method, a first area location information recording area for recording location information of the first area on the disk, and a second area location information recording area for recording location information of the second area on the disk, the method including the steps of:
reproducing information recorded in the first area in accordance with the location information of the first area on the disk recorded in the first area location information recording area, and outputting a reproduced signal of the first area;
reproducing information recorded in the second area in accordance with the location information of the second area on the disk recorded in the second area location information recording area, and outputting a reproduced signal of the second area;
detecting an area having the reflecting film partly removed, in accordance with the reproduced signal of the first area;
detecting a pit which is different from the pit satisfying the requirements of the predetermined modulation method, in accordance with the reproduced signal of the second area; and
judging whether or not the information recorded on the optical disk should be reproduced, in accordance with results detected by the two steps of detecting.
In the above-mentioned method, the step of reproducing information recorded in the first area preferably includes the step of reproducing information recorded in the first area in a defocus state.
In the above-mentioned method, the step of reproducing information recorded in the first area preferably includes the step of reproducing the information recorded in the first area by performing tracking an area located between two adjacent tracks.
In the above-mentioned method, the step of detecting the area having the reflecting film partly removed preferably includes the step of detecting whether or not the reflecting film is removed on the two adjacent tracks.
According to a still further aspect of the present invention, there is provided an apparatus for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, and a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method, the apparatus comprising:
a first area detecting circuit for detecting the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the first area, and outputting a first detecting signal;
a second area detecting circuit for detecting the second area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on the optical disk should be reproduced, in accordance with the first and second detecting signals.
According to a more still further aspect of the present invention, there is provided an apparatus for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method, a first area location information recording area for recording location information of the first area on the disk, and a second area location information recording area for recording location information of the second area on the disk, the apparatus comprising:
a first detecting window generating circuit for generating a first detecting window signal in accordance with the location information of the first area on the disk recorded in the first area location information recording area;
a second detecting window generating circuit for generating a second detecting window signal in accordance with the location information of the second area on the disk recorded in the second area location information recording area;
a first area detecting circuit for detecting the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the first area, and outputting a first detecting signal;
a second area detecting circuit for detecting the second area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on the optical disk should be reproduced, in accordance with the first detecting signal in a valid time interval of the first detecting window signal, and the second detecting signal in a valid time interval of the second detecting window signal.
In the above-mentioned apparatus, the first area detecting circuit preferably comprises a first comparator for comparing the reproduced signal from the optical disk upon reproducing information recorded in the first area, with a predetermined first threshold value, and outputting a first comparison result signal.
In the above-mentioned apparatus, the second area detecting circuit preferably comprises:
a second comparator for comparing the reproduced signal from the optical disk upon reproducing information recorded in the second area, with a predetermined second threshold value, and outputting a second comparison result signal;
a third comparator for comparing the reproduced signal from the optical disk upon reproducing information recorded in the second area, with a predetermined third threshold value, and outputting a third comparison result signal; and
an arithmetic logic circuit for performing a logic operation between the second comparison result signal and the third comparison result signal, and outputting a logic operation result signal.
In the above-mentioned apparatus, the first area detecting circuit preferably detects the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded on a track including the first area, and a reproduced signal from the optical disk upon reproducing information recorded on a further track including the first area and adjacent to the track, and outputs the first detecting signal.
According to a further aspect of the present invention, there is provided a method for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, the method including the steps of:
detecting the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the first area, and outputting a first detecting signal; and
judging whether or not the information recorded on the optical disk should be reproduced, in accordance with the first detecting signal.
In the above-mentioned method, the step of detecting the first area and outputting the first detecting signal preferably includes the step of:
detecting the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded on a track including the first area, and a reproduced signal from the optical disk upon reproducing information recorded on a further track including the first area and adjacent to the track, and outputting the first detecting signal.
In the above-mentioned method, the step of detecting the first area and outputting the first detecting signal preferably includes the step of:
judging whether or not the first area is detected in accordance with whether or not a first number of data from a predetermined sector address to the detected first area, which is counted based on the reproduced signal from the optical disk upon reproducing information recorded on the track including the first area, substantially coincides with a second number of data from the sector address to the detected first area, which is counted based on the reproduced signal from the optical disk upon reproducing information recorded on a further track including the first area and adjacent to the track.
According to a still further aspect of the present invention, there is provided an apparatus for reproducing information recorded on an optical disk which is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits, the optical disk comprising a first area having a reflecting film partly removed, the apparatus comprising:
detecting means for detecting the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded in the first area, and outputting a first detecting signal; and
judging means for judging whether or not the information recorded on the optical disk should be reproduced, in accordance with the first detecting signal.
In the above-mentioned apparatus, the detecting means preferably detects the first area in accordance with a reproduced signal from the optical disk upon reproducing information recorded on a track including the first area, and a reproduced signal from the optical disk upon reproducing information recorded on a further track including the first area and adjacent to the track, and outputs the first detecting signal.
In the above-mentioned apparatus, the detecting means preferably judges whether or not the first area is detected in accordance with whether or not a first number of data from a predetermined sector address to the detected first area, which is counted based on the reproduced signal from the optical disk upon reproducing information recorded on the track including the first area, substantially coincides with a second number of data from the sector address and the detected first area, which is counted based on the reproduced signal from the optical disk upon reproducing information recorded on a further track including the first area and adjacent to the track.